As a network interface for realizing Broadband Aspects of Integrated Services Digital Network (B-ISDN), there is a Synchronous Optical NETwork/Synchronous Digital Hierarchy (SONET/SDH) method.
In a communication network of the SONET/SDH method (hereinafter, also described SONET/SDH network), a data signal is transmitted by using a data frame (transmission frame) having an overhead section and a payload section. The overhead section has, for example, a pointer for indicating a relative start position of the payload (data main body) contained in the payload section. In this way, the transmission frame contains the payload by setting any position of the payload section as the start position of the payload.
Here, SONET/SDH is a collective term of the Synchronous Optical NETwork (SONET) and the Synchronous Digital Hierarchy (SDH).
SONET is standardized by the American National Standards Institute (ANSI). The basic unit of multiplexing is 51.84 Mbps, which may be called OC-1 (Optical Carrier-level 1). A channel in which signals of 51.84 Mbps are multiplexed is represented as OC-n (n is a positive integer).
On the other hand SDH is standardized by the International Telecommunications Union (ITU). The basic unit of multiplexing is 155.52 Mbps, which may be called STM-1 (Synchronous Transmission Module-level 1). A channel in which signals of 155.52 Mbps are multiplexed is represented as STM-m (m is a multiple of 4).
The above described SONET/SDH network realizes high-speed communication by multiplexing a plurality of channels hierarchically.
Wavelength Division Multiplexing (WDM) for transmitting a plurality of optical signals having different wavelengths is known. In a communication network of the WDM method, since a plurality of optical transmission paths are virtually included in one transmission path, different types of optical signals and different protocols of communication are overlapped in one path.
In addition, a communication network in which SONET/SDH and WDM are combined (hereinafter, called a SONET/SDH/WDM network) is known. In the SONET/SDH/WDM network, for example, a plurality of SONET/SDH transmission frames are optically converted by light sources having different wavelengths, wavelength-multiplexed, and thereafter transmitted to a transmission path. Therefore, the SONET/SDH/WDM network has, for example, a configuration in which a plurality of communication apparatuses (hereinafter, called nodes) are connected by transmission paths (for example, optical fibers).
For example, a node for transmission in the SONET/SDH/WDM network converts input signals (for example, OC-n signals of SONET or the like) into optical signals having a different wavelength for each channel, multiplexes these optical signals by using an optical multiplexer, and transmits the multiplexed optical signal into one optical fiber. On the other hand, for example, a node for reception demultiplexes the optical wavelength-multiplexed signal into each wavelength by using an optical demultiplexer, and performs reception processing on the demultiplexed signals. Each node includes, for example, a cross-connect function for transmitting an optical signal from a start node to an end node of a communication path.
The cross-connect function is a function for transmitting a signal inputted into an input port of a node to a predetermined output port on the basis of cross-connect information set in advance.
For example, a network administrator controls input/output of an optical signal in a node by setting cross-connect information in the node. It is known that a signal transmission path is established between nodes in this way.
In addition, it is known that a Generalized Multi-Protocol Label Switching (GMPLS) protocol is used in the SONET/SDH/WDM network. By using the GMPLS protocol, for example, it is possible to operate a communication network in an autonomous-decentralized way.
As a technique rerated to GMPLS, a method in which, in a communication network including nodes having GMPLS and nodes not having GMPLS, all settings necessary for GMPLS control are preliminarily set in the nodes not having GMPLS is known, in Japanese Laid-open Patent Publication No. 2007-318288.
Also, a method in which a wavelength path is added or deleted in accordance with a result of traffic calculation is known, in Japanese Laid-open Patent Publication No. 2006-157102.